MCH, Gauss Barrel and Armageddon.

[Ephier]

The Gauss Barrel is centered on the top barrel only because it's based on the Gatling gun. The three barrels rotate just like a machine gun - only the currently topmost barrel will fire the shell while the other two barrels are in a state of automated reloading. In addition, multiple barrels set up like this allows each barrel to cool off faster which in RL allows a faster rate of fire.

If the Barrel were centered (assuming it works to magnetically increase the velocity of bullets passing through it or whatever the magical equivalent is), the bullet would do some crazy bad physics. So while it looks weird, it's because it's based on how a gun like that would actually fire.

Take a look at the ferdinand and get back to me on the realism. This is a game and one of the most important MCH weapons in the game looks dumb because of what appears to be a design flaw. I highly doubt the realism of the barrels rotation was thought out when designing this weapon.